Lunatic: ksqrt, with timing and value test.

The latter shows that "int32_t ksqrt(int32_t)" also copes with values in the
range INT32_MIN..-1, effectively interpreting them as uint32_t (i.e. adding
2**32).  However, this should not be relied on from CON.

git-svn-id: https://svn.eduke32.com/eduke32@2790 1a8010ca-5511-0410-912e-c29ae57300e0

polymer/eduke32/source/lunatic/defs.ilua

@@ -471,6 +471,10 @@ playerdata_t g_player[MAXPLAYERS];
 ]]
 
 -- functions
+ffi.cdef[[
+int32_t ksqrt(int32_t num);
+]]
+
 ffi.cdef "double gethitickms(void);"
 
 local ffiC = ffi.C

polymer/eduke32/source/lunatic/dynsymlist

@@ -26,6 +26,7 @@ nextspritestat;
 headsectbunch;
 nextsectbunch;
 
+ksqrt;
 hitscan;
 
 actor;

polymer/eduke32/source/lunatic/test.elua

@@ -127,6 +127,7 @@ gameevent(gv.EVENT_JUMP,
 
 gameevent(gv.EVENT_ENTERLEVEL,
           function()
+              -- NOTE: times are for helixhorned (Core2Duo 3GHz)
               local i
               local N = 1e6
               local t = gv.gethitickms()
@@ -137,9 +138,28 @@ gameevent(gv.EVENT_ENTERLEVEL,
 
               t = gv.gethitickms()-t
 
-              -- NOTE: for me (helixhorned), about 40 ns per call
+              -- x86: 40ns/call, x86_64: 290 ns/call
               printf("%d gethitickms() calls took %.03f ms (%.03f us/call)",
                      N, t, (t*1000)/N)
+
+              local sum=0
+              t = gv.gethitickms()
+              for i=1,N do sum = sum+gv.ksqrt(i) end
+              t = gv.gethitickms()-t
+              -- x86_64: 14ns/call
+              printf("%d ksqrt() calls took %.03f ms (%.03f us/call) [sum=%f]",
+                     N, t, (t*1000)/N, sum)
+
+              sum=0
+              t = gv.gethitickms()
+              for i=1,N do sum = sum+math.sqrt(i) end
+              t = gv.gethitickms()-t
+              -- x86_64: 7ns/call
+              printf("%d math.sqrt() calls took %.03f ms (%.03f us/call) [sum=%f]",
+                     N, t, (t*1000)/N, sum)
+
+              printf("sqrt(0xffffffff) = %f(ksqrt) %f(math.sqrt)",
+                     gv.ksqrt(-1), math.sqrt(0xffffffff))
           end
          )